Such a mechanism is described in EP-A-0331325 comprising a support member, a drive shaft rotatably mounted on and extending from the support member, means for rotatably driving the drive shaft, carrier means rotatable with the drive shaft, at least one support shaft rotatable on the carrier means substantially parallel to the drive shaft, whereby the support shaft can orbit round the drive shaft, means for controlling the rotational disposition of the support shaft with respect to the carrier means, at least one suction cup attached to the support shaft, means for producing a vacuum, means alternatively connecting the suction cup with the vacuum-producing means and the atmosphere, the means for controlling the support shaft including means causing the suction cup while connected with the vacuum producing means to contact an article at the discharge opening of the magazine, extract the article from the magazine, and transfer the article to the receiving station, whereupon the suction cup is connected with the atmosphere to release the article to the receiving station, characterised in that the means for controlling the at least one support shaft comprises on the one hand, a pinion secured coaxially to the support shaft, and an arcuate rack secured to the support member in such a position as to act upon the pinion to create a partial path of the at least one suction cup with a “node point” at the discharge opening of the magazine; and, on the other hand, a cam follower on an arm extending laterally from the support shaft, and a cam track secured to the support member and of such an operative extent as to act upon the cam follower when the arcuate rack is not acting on the pinion, the profile of the cam track being such as to cause the suction cup to move past the receiving station in the same direction as the conveyor with the article generally parallel to the conveyor.
Thus, the suction cup “plucks” each article from the magazine, but instead of merely dropping the article at the receiving station, the suction cup imparts to the article a major component of motion in the direction of movement of the conveyor, with consequent better placement of the article on the conveyor. The flexibility of design in suction cup path afforded by the combination of the ratio of the rack-and-pinion drive, the disposition of the rack, and the profile of the operative extent of the cam track, allows for a wide choice of article length and disposition of magazine, whilst avoiding interference between the magazine or the conveyor with the article while it is being transferred. This is particularly important when the conveyor has flights for the timed positioning of the articles in relation to a subsequent operation, such as when the article is a sleeve carton presented on the conveyor in open condition ready for end loading with a product at a subsequent station.